diff --git a/src/gallium/auxiliary/rtasm/rtasm_x86sse.c b/src/gallium/auxiliary/rtasm/rtasm_x86sse.c
index 9fc3a712244..1a5678f8407 100644
--- a/src/gallium/auxiliary/rtasm/rtasm_x86sse.c
+++ b/src/gallium/auxiliary/rtasm/rtasm_x86sse.c
@@ -174,7 +174,7 @@ static void do_realloc( struct x86_function *p )
  */
 static unsigned char *reserve( struct x86_function *p, int bytes )
 {
-   if (p->csr + bytes - p->store > (int) p->size)
+   if (p->csr - p->store + bytes > (int) p->size)
       do_realloc(p);
 
    {